Due to the defects in the liquid crystal display (Liquid Crystal Display, LCD) process, it often leads to the uneven brightness of the produced liquid crystal display panel to form a variety of mura (mura refers to the uneven brightness of the display, resulting in phenomenon of various marks).
For promoting the uniformity of the display panel brightness, there are mura compensation methods at present, i.e. capturing the gray scale screen (the white screens of different brightnesses) with the external camera, and comparing with the brightness of the center position of the display panel to calculate the differences between the brightnesses of the surrounding region and the center position, and then, reversely compensating the gray scales (reducing the gray scale for the region which is brighter than the center position for reducing the brightness; raising the gray scale for the region which is darker than the center position for raising the brightness) of the mura positions to enable the display panel as a whole have a relatively uniform brightness.
The general reverse compensation data is stored in the data memory (flash). Meanwhile, in order to reduce the design cost, the data memory does not store the gray-level compensation data for each pixel. The general practice is to implement compression for regions of n*n pixels (such as 8*8 pixels). Typically, the gray scale compensation data for one pixel is stored in the data memory for each region. The gray scale compensation data of other pixels in the region is calculated by linear interpolation.
The display panel (3840*2160 pixels UHD, representing regions of 3840 pixels and 2160 pixels) of (Ultra High Definition) resolution is described as an example. Please refer to FIG. 1. The compression is implemented for 8*8 pixels to form 480*270 regions (the square dotted line in figure forms one region). The data memory stores the mura compensation data corresponding to the pixels (marked with circles) at the intersection positions of the 1st row of pixels, the 9th row of pixels, the 17th row of pixels, . . . , the 2145th row of pixels, and the 2153th row of pixels with the 1st column of pixels, the 9th column of pixels, the 17th column of pixels, . . . , the 3825th column of pixels, and the 3833th column of pixels, which includes 480*270 mura compensation data. Besides, for calculating and obtaining the mura compensation data corresponding to the 3834th column to the 3840th column of pixels and calculating the mura compensation data corresponding to the 2154th row to the 2160th row of pixels, the mura compensation data corresponding to the 3841th column of the pixel (the virtual pixels marked in the circles) is calculated and obtained with the stored mura compensation data corresponding to the 3825th column of pixels and the stored mura compensation data corresponding to the 3833th column of pixels to have 270 mura compensation data. The mura compensation data corresponding to the 2161th row of the pixel (the virtual pixels marked in the circles) is calculated and obtained with the stored mura compensation data corresponding to the 2145th row of pixels and the stored mura compensation data corresponding to the 2153th row of pixels to have 480 mura compensation data. Accordingly, the data memory needs to store a total of 481*271 mura compensation data. The mura compensation data of the other pixels is calculated and obtained by the linear interpolation of the sequence controller (Tcon IC) according to the present 481*271 mura compensation data.
The specific calculations of the other pixels are as follows, and please continue referring to FIG. 1. The region formed by 8*8 pixels of the 1st column to the 8th column is illustrated for explanation. In this region, as known, the mura compensation value corresponding to the pixel at the intersection of the 1st column of pixels and the 1st row of pixels is A′, and the mura compensation value corresponding to the pixel at the intersection of the 9st column of pixels and the 1st row of pixels is B′, and the mura compensation value corresponding to the pixel at the intersection of the 1st column of pixels and the 9st row of pixels is C′, and the mura compensation value corresponding to the pixel at the intersection of the 9st column of pixels and the 9st row of pixels is D′, and the mura compensation value corresponding to the pixel e′ is E′, and the mura compensation value corresponding to the pixel f′ is F′, and the mura compensation value corresponding to the pixel g′ is G′, and E′, F′ and G′ are calculated by linear interpolation as follows:E′=[(8−Y′)*A′+Y′*C′]/8;F′=[(8−Y′)*B′+Y′*D′]/8;G′=[(8−X′)*E′+X′*F′]/8.
X′ and Y′ are the row number and the column number of the corresponding pixel relative to the pixel at the crossing position of the first column and the first row.
With further reference to the above calculation method, the mura compensation data calculation of the 3834th column to the 3840th column of pixels and the 2154th row to the 2160th row of pixels requires the mura compensation data corresponding to the 3841th column of pixels and the 2161th row of pixels. Therefore, 481*271 mura compensation data need to be stored. Because the data memory needs storing 481*271 mura compensation data, the amount of data stored is larger, resulting in that the data storage space of the data memory needs to be larger, thus increasing the cost.